Electric motors nowadays are applied in almost all technical fields. One therefore strives to increase the efficiency of such motor and thus their economic efficiency. Measures increasing the efficiency are worthwhile, in particular with motors which run for a long operational time period, such as drive motors of pump units, compressors, ventilators or likewise, since corresponding savings in consumption are to be expected.
Modem electric motors have an electronic control which is connected in series to the actual motor in order from the essentially constant direct or alternating voltage available on the mains side to produce a voltage suitable for the operation of the motor. For this one typically applies transformers, for example in the form of frequency converters which have an input circuit in which the alternating voltage is rectified, an intermediate circuit in which the desired voltage level is set, and a power circuit in which the intermediate circuit voltage is led to the motor windings in a suitably controlled manner. Asynchronous motors for example are operated in this manner but also permanent magnet motors are electronically commutated.
For increasing the efficiency of units, the technical exploitation of their waste heat is counted as belonging to the state of the art, be it by way of additional heat exchangers, heat pumps or likewise. These measures at present are not suitable for motors of a small construction type for reasons of costs.
The application of semiconductor elements, so-called Seebeck elements is counted as belonging to the state of the art for exploiting the waste heat. It is known from the U.S. Pat. No. 6,019,098 to use such Seebeck elements for exploiting the waste heat of a boiling vessel. From U.S. Pat. No. 5,419,780 it is known to use the waste heat of an electronic component for producing current for operating a ventilator which then cools this component. It is known from U.S. Pat. No. 4,753,682 to use the waste heat of a combustion motor for producing current by way of Seebeck elements. The exploitation of waste heat of electronic components by way of one or more Seebeck elements, and the supply of the energy gained at the same time to the componentry in a useful manner is also counted as belonging to the state of the art (U.S. Pat. 6,066,002).
The use of semiconductor elements of the previously mentioned type, specifically Peltier elements for the targetted cooling is also counted as belonging to the state of the art. It is known from U.S. Pat. No. 5,486,728 to cool a micromotor by way of such Peltier elements. These Peltier elements however require an additional energy supply and thus worsen the efficiency.